1. Field of the Invention
The present invention relates to a data processing apparatus for accessing a recording medium and reading and writing data thereon, and in particular to a data processing apparatus for accessing the recording medium based on access control information.
2. Related Arts
A recording medium having a large memory capacity, such as an optical disk or a magneto-optical disk, is an appropriate medium for recording data, such as image information for films and music information, which are copyright protected. When the use of data recorded on a recording medium is permitted, the access permission conditions, such as the limitations of accessible range of data and/or the number of accessible times to data, can be set.
These access permission conditions are recorded as access control information in a predetermined area on a recording medium, for example. A data processing apparatus reads the access control information and accesses data based on that information. To prevent such access control information from being rewritten freely, the information can be accessed only when, for example, a password which is input from an upper level apparatus, connected to a data processing apparatus, matches a password included in the access control information.
However, if the password is decoded by specific means, the access control information itself can be accessed and can be illegally rewritten. To prevent this from occurring, therefore, the predetermined area where the access control information is recorded may be set as a non-rewritable area. However, the following problem is encountered at this case. That is, in case that accessible times for limiting the number of times of access to a predetermined data area is established as the access control information, the accessible times can not be updated. Specifically, since accessed times must be counted each access to the data area and, the number of the remaining accessible times must be updated. However, in case that the predetermined area for the access control information has been set as the non-rewritable area, the updating process can not be performed. Therefore, a demand exists for ensuring the security of access control information which must be updated.
It is one objective of the present invention to provide a data processing apparatus for ensuring the security of access control information which needs to be updated, and an access control method therefor.
To achieve the above objective, according to the present invention, there is provided a data processing apparatus for accessing a recording medium for reading and writing of data comprising:
a setting unit for setting a predetermined area on said recording medium as a dedicated area for additional recording, in which the updating of recorded data is inhibited but in which the writing of data in a non-recorded portion is permitted;
a recording unit for recording access control information in said dedicated area; and
an access controller for controlling access to said recording medium based on said access control information recorded in said dedicated area.
Thus, since the updating process which is required for the access control information recorded in the access control area can be performed, and since the illegal rewriting of the access control information can be prevented, ensured security is provided for the access information.
For example, in case that the access control information includes accessible count information which is the number of accessible times for recording medium, each time the recording medium is accessed, the access controller subtracts the accessible count information and the recording unit records the value of remaining accessible count information in the non-recorded portion of the dedicated area. In this case, the access controller controls the access to the recording medium based on the minimum value of the accessible count information recorded in the dedicated area. The recording unit may record accessed count information which is the number of accessed times in the non-recorded portion of the dedicated area, the accessed count information is added each time the access controller accesses the recording medium. In this case, the access controller controls the access to the recording medium based on the maximum value of the accessed count information recorded in the dedicated area.
When a plurality of data are recorded in a data area on the recording medium, the access control information is established for at least one data which is accessible in the data area of the recording medium. Thus, the access control information is established for a part of the data area.
Furthermore, it is preferable byte units be employed for the recording the access control information in the predetermined area by the recording unit, and that likewise the access controller read the access control information by the byte units. Therefore, compared with the recording of data by sector units, each of which is normally composed of several hundred bytes, a comparatively small amount of access control information can be efficiently recorded in the access control area.
Further, to achieve the above objective, there is provided a access control method for accessing a recording medium for reading and writing of data comprising the steps of:
recording access control information in a dedicated area for additional recording on said recording medium, in which the updating of recorded data is inhibited but in which the writing of data in a non-recorded portion is permitted; and
controlling access to said recording medium based on said access control information recorded in said dedicated area.